In modern semiconductor device applications, numerous devices are packed onto a single small area of a semiconductor substrate to create an integrated circuit. For the circuit to function, many of these individual devices may need to be electrically isolated from one another. Accordingly, electrical isolation is an important and integral part of semiconductor device design for preventing the unwanted electrical coupling between adjacent components and devices.
As the size of integrated circuits is reduced, the devices that make up the circuits must be positioned closer together in order to comply with the limited space available on a typical semiconductor substrate. As the industry strives towards a greater density of active components per unit area of semiconductor substrate, effective isolation between circuits becomes all the more important.
The conventional method of isolating circuit components in modern integrated circuit technology takes the form of trench isolation regions etched into a semiconductor substrate. Trench isolation regions are commonly divided into three categories: shallow trenches (STI) (trenches less than about 1 micron deep); moderate depth trenches (trenches of from about 1 to about 3 microns deep); and deep trenches (trenches greater than about 3 microns deep). Once the trench isolation regions are etched in the semiconductor substrate, a dielectric material is deposited to fill the trenches. As the density of components on the semiconductor substrate increased, the widths of the trenches decreased until the process of flowing dielectric material into the trenches developed problems.
Trench isolation regions, particularly STI regions, can develop undesirable voids in the dielectric material during the process to fill the trenches. As the dielectric material flows to an edge between a substrate surface and a sidewall of the trench, constrictions develop at the top of trenches due to the narrow opening in the trench. As the dielectric material flows into the trench, the constrictions can develop into voids moving into the trench with the dielectric material. Voids lower the dielectric characteristics of the dielectric material used and introduce structural instabilities in subsequent processes. Accordingly, voids in the dielectric material filling an isolation trench region are highly undesirable.